Preparation of high-quality thick AlN layer on nanopatterned sapphire substrates with sputter-deposited annealed AlN film by hydride vapor-phase epitaxy

Abstract

A crack-free aluminum nitride (AlN) layer of 9 ± 1 μm thickness was grown on a nanopatterned sapphire substrate (NPSS) with a sputter-deposited AlN buffer layer. The buffer layer was thermally annealed and AlN was regrown by hydride vapor-phase epitaxy (HVPE). The dependence of the crystallinity of HVPE-grown AlN layers on the growth temperature was investigated. It was found that undesired misaligned AlN growth can be prevented by choosing an appropriate growth temperature. The full widths at half maximum of the (0002)- A nd (10-12)-plane X-ray rocking curves were improved to as low as 102 and 219 arcsec, respectively, by applying an NPSS with a sputter-deposited annealed AlN film. Compared with substrates without nanopatterning, the NPSS was also effective for suppressing cracks owing to the formation of voids at the interface of the HVPE-grown AlN layer and NPSS template.